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Space Shuttle computer has 1MB of RAM

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Re: Space Shuttle computer has 1MB of RAM

#31

Post by kjhgfvgbjnm »

Groxx wrote: post #30
kjhgfvgbjnm wrote: post #27

Earlier quoted context omitted.

The Burj Dubai, like any other structure is full of bugs. The point of engineering is to make a system that is resilient to a certain level of faults. That's why the tower doesn't collapse if there is a 0.1 mm crack in one of the bolts.

It also depends on how you define a "bug". A car that crumples too much and injures the driver when hit at this angle or that angle within these speeds could be considered a bug. In which case, counting the number of knobs that fall off, plastic that cracks, and parts that wear out prematurely, not to mention discoveries of toxic fumes / paint / etc, cars do have thousands of bugs.

The main problem with software 'engineering' is the fragility of software. In a structure you know there will be cracks, so you choose a material that is ductile enough that a crack can't grow to dangerous size in the lifetime of the component. The problem with software is that generally a single bit wrong is a total failure.

I was involved in a case with a turbine blade fracture. The user claimed that there must have been a flaw, and yes the crack must have started at a single atom sized crystal flaw in the meta. But the choice of alloy was such that the crack would have grown at a rate which means it was under the failure size for at least twice the inspection interval - where the customer missed it.

Re: Space Shuttle computer has 1MB of RAM

#32

Post by khafra »

kjhgfvgbjnm wrote: post #31
Groxx wrote: post #30

Earlier quoted context omitted.

It also depends on how you define a "bug". A car that crumples too much and injures the driver when hit at this angle or that angle within these speeds could be considered a bug. In which case, counting the number of knobs that fall off, plastic that cracks, and parts that wear out prematurely, not to mention discoveries of toxic fumes / paint / etc, cars do have thousands of bugs.

The main problem with software 'engineering' is the fragility of software. In a structure you know there will be cracks, so you choose a material that is ductile enough that a crack can't grow to dangerous size in the lifetime of the component. The problem with software is that generally a single bit wrong is a total failure. I was involved in a case with a turbine blade fracture. The user claimed that there must hav…

Perhaps the problem with software is that, after the original QA process, there's seldom a regular inspection except adversarially.

Re: Space Shuttle computer has 1MB of RAM

#33

Post by jonknee »

Groxx wrote: post #25
tomkinstinch wrote: post #6

Here is an article about developing the 'perfect' software that runs the shuttle: "They Write the Right Stuff" http://www.fastcompany.com/node/28121/print

Must be nice to have such clearly defined problems. edit: woah, feature-fail == bug? Why'd it take them until 2007 to not have to reboot whenever they reached a new year? I'd call that a rather significant, costly bug, even if they don't, and it may very well be one of the longest-running in actively-developed software.

I'd imagine they go by if it's not in the spec it's not a bug. They can't do something not in the spec. It was a known limitation, not a "bug".

Re: Space Shuttle computer has 1MB of RAM

#35

Post by Groxx »

jonknee wrote: post #33
Groxx wrote: post #25

Earlier quoted context omitted.

Must be nice to have such clearly defined problems. edit: woah, feature-fail == bug? Why'd it take them until 2007 to not have to reboot whenever they reached a new year? I'd call that a rather significant, costly bug, even if they don't, and it may very well be one of the longest-running in actively-developed software.

I'd imagine they go by if it's not in the spec it's not a bug. They can't do something not in the spec. It was a known limitation, not a "bug".

It was a known limitation, not a "bug".

That pretty strongly implies that all known strange-behavior is not a bug. Also, all known bugs are not bugs, as they can be known and worked around.

If you had to shut down your computer during the year cross-over, would you consider it a bug? Or what if you couldn't go on your business trip because of the year cross-over.

And a bug in the spec is still a bug. Oversights in specifications are equivalent to oversights in programming.

Re: Space Shuttle computer has 1MB of RAM

#37

Post by abstractbill »

kjhgfvgbjnm wrote: post #31
Groxx wrote: post #30

Earlier quoted context omitted.

It also depends on how you define a "bug". A car that crumples too much and injures the driver when hit at this angle or that angle within these speeds could be considered a bug. In which case, counting the number of knobs that fall off, plastic that cracks, and parts that wear out prematurely, not to mention discoveries of toxic fumes / paint / etc, cars do have thousands of bugs.

The main problem with software 'engineering' is the fragility of software. In a structure you know there will be cracks, so you choose a material that is ductile enough that a crack can't grow to dangerous size in the lifetime of the component. The problem with software is that generally a single bit wrong is a total failure. I was involved in a case with a turbine blade fracture. The user claimed that there must hav…

The problem with software is that generally a single bit wrong is a total failure.

This doesn't mesh with my experience to be honest. I often come across code that contains nasty bugs but is still somehow working accidentally. And even more often, there are bugs that stop just one feature from working while the rest of a large system pretty much acts as if the bug didn't exist.

Re: Space Shuttle computer has 1MB of RAM

#38

Post by ugh »

icefox wrote: post #11

"Similarly, the Russian Soyuz capsule’s computer ran on only 6 kilobytes of RAM until it was replaced with newer systems in 2003, which most probably was the cause of its subsequent crash-landing in Kazakhstan." Really? Really?

Really (http://en.wikipedia.org/wiki/Soyuz_TMA-1). That was the first flight of the new Soyuz TMA with a glass cockpit.

The capsule’s failsafe mechanisms where triggered and the it fell back to the harsher ballistic reentry instead of the normal controlled one (nobody was harmed). It seems that a system which has been in use since 1979 somehow got confused by the sensory data. Some sort of odd bug, they have never been able to reproduce it.

Fallback to ballistic reentries also happened later with TMA-10 and TMA-11 – in those two cases a damaged cable and a pyro bolt malfunction (which nearly got the crew killed) were responsible respectively.

Re: Space Shuttle computer has 1MB of RAM

#39

Post by ChillyWater »

code_duck wrote: post #19

I wonder how that was all written. Is it mainly hardware, assembly or a language such as Forth?

Most of it is written in a custom language called HAL/S (High Level Assembly Language / Shuttle). Some of the nitty gritty is written in assembly.

HAL/S looks a little bit like basic or FORTRAN. It was designed to be very readable and uses some interesting formatting. When you print out a module (lets say GG1ASC), it uses three lines for each line of code so that the superscripts and subscripts are above and below like they should be.

Re: Space Shuttle computer has 1MB of RAM

#40

Post by jonknee »

Groxx wrote: post #35
jonknee wrote: post #33

Earlier quoted context omitted.

I'd imagine they go by if it's not in the spec it's not a bug. They can't do something not in the spec. It was a known limitation, not a "bug".

It was a known limitation, not a "bug". That pretty strongly implies that all known strange-behavior is not a bug. Also, all known bugs are not bugs, as they can be known and worked around. If you had to shut down your computer during the year cross-over, would you consider it a bug? Or what if you couldn't go on your business trip because of the year cross-over. And a bug in the spec is still a bug. Oversights in sp…

If I commissioned a computer to be made that wasn't supposed to be able to span the new year then no I would not consider it a bug that it could not span the new year. Sure it would be great if it would do that (though only if I had asked that it would), but as long as it behaves exactly as expected then I'm happy. No astronauts die and my budget won't cut. Success.

A similar parallel in consumer computing is switchable graphics. The first models that supported this required a reboot to accomplish it. That wasn't a bug, just part of the plan. They have since gotten more advanced and allow switching without a restart.

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